Already facing opposition from a swathe of Tory MPs to proposals to HS2, the PM is now facing the threat of a revolt over the estuary airport issue. Six backbenchers have written to Cameron urging him to kill the “Boris Island” scheme off, warning that it would cause huge environmental damage to the area. It is understood that several ministers and Tory whips, who are not signatories to the letter, are also unhappy at the prospect of a massive new hub airport either on the Isle of Grain or on reclaimed land in the Thames Estuary. The MPs signing the letter are Remhan Chishti (Gillingham and Rainham); Tracey Crouch (Chatham & Aylesford); Gordon Henderson (Sittingbourne & Sheppey); Adam Holloway (Gravesham); Gareth Johnson (Dartford) and Mark Reckless (Rochester & Strood).

Already facing opposition from a swathe of Tory MPs to proposals to run a high speed rail line through the Chilterns, Northamptonshire and Warwickshire, the Prime Minister is now facing the threat of a revolt over a second flagship transport policy.

Six backbenchers have written to then Prime Minister urging him to kill the “Boris Island” scheme off, warning that it would cause huge environmental damage to the area.

It is understood that several ministers and Tory whips, who are not signatories to the letter, are also unhappy at the prospect of a massive new hub airport either on the Isle of Grain or on reclaimed land in the Thames Estuary.

In October 2010 Mr Cameron said that the Government had “no plans” to build an airport in the Thames Estuary.

But earlier this month the Prime Minister performed a U-turn and announced that the Government would carry out a feasibility study examining whether a new multi-runway hub airport should be built.

“The proposals for an airport in the Thames Estuary do not appear to be supported by the public or indeed by the aviation industry,” the MPs told the Prime Minister.

“If any such proposal were to go ahead it would have an enormous effect on the lives of hundreds of thousands of residents living in the wider Thames Estuary region and devastate an area of global environmental significance.”

The letter has been signed by Remhan Chishti, Tory MP for Gillingham and Rainham; Tracey Crouch MP for Chatham and Aylesford; Gordon Henderson MP, for Sittingbourne & Sheppey; Adam Holloway, MP for Gravesham; Gareth Johnson, MP for Dartford and Mark Reckless MP for Rochester and Strood.